1. Field of the Invention
The present invention relates to a two-wheeled motorcycle of a type in which a power unit is enveloped by a shell constituting at least a part of the chassis.
2. Description of the Prior Art
In two-wheeled motorcycles, the acceleration performance, driving performance and various other performances are largely affected even by a slight change of the weight, and various measures have been taken to reduce the weight of the two-wheeled motorcycles. However, the reduction of weight of prior art designs has almost reached a limit in the cases of conventional construction of two-wheeled motorcycles in which the chassis frame is constructed of steel pipes or plates. The chassis frame is generally made with sufficient strength by itself and a power unit is mounted on the chassis frame. In such cases, further lightening of the frame to reduce weight thereof, weakens the strength thereof to the point where the frame is useless.